Display and electronic devices of various types are being widely utilized. A considerable fraction of total power used to drive small electronic devices, such as laptop computers or televisions, is consumed by the video display. Flat panel displays are becoming an integral part of these devices since they are lighter and less bulky compared to conventional cathode ray tubes (CRTs). Liquid crystal displays are commercially available and are mainly used for portable computers. The disadvantages of liquid crystal displays include high energy consumption, high cost of production, low intensity, limited viewing angle, and difficulties associated with large diameter display production.
Among a few alternatives to the active matrix liquid crystal display (AMLCD) is the field emission display. These displays traditionally rely on emission of electrons from arrays of sharp tips. Each tip serves the function of a filament in a traditional CRT by providing a stream of electrons to excite a phosphor on a nearby screen. The ease of electron emissions, and therefore the reduction in energy consumption of the display, depends on the work function of material and sharpness of the tips. These arrays of tips are expensive and difficult to manufacture on small scales and, so far, have been prohibitively expensive for commercial applications. Recently, a process and apparatus has been developed which enables the deposition of low work function material on the field emission tips, and is described and claimed in copending U.S. application Ser. No. 09/080,109, filed May 18, 1998 entitled "Low Work Function Surface Layers Produced by Laser Ablation Using Short-Wavelength Photons," assigned to the same assignee.
Several manufacturers have proposed the use of planar electron emitters in a simple diode geometry to overcome said manufacturing difficulties relative to arrays of sharp electron emission tips. One recent approach to the use of planar electron emitters is described and claimed in copending U.S. application Ser. No. 09/080,110, filed May 18, 1998, now U.S. Pat. No. 6,162,707 entitled "Low Work Function, Stable Compound Clusters and Generation Process," assigned to the same assignee. The production of stable, low work function materials on flat substrates will enable the introduction of this technology, thus, in addition to the compound cluster approach of above-referenced application Ser. No. 09/080,110, the present invention provides for the generation of low work function, stable compound thin films produced by simultaneously laser ablating a silicon target, for example, and thermal evaporating an alkali metal, such as cesium, into an oxygen environment. The compound thin films may be deposited on a substrate, such as silicon, which is patterned to produce a pattern of compound thin films on the substrate. The work functions of the compound thin films (for example, Si/Cs/O films) can be varied by changing the ratio of the components. Tests conducted on the compound thin films have established a low work function and that the films are stable up to 500.degree. C.